Resin Insulating Substrate for Thin Flexible LCD Panels
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Solution Overview
Problem
Current liquid crystal display devices face challenges in reducing the thickness and weight of the substrate while maintaining heat resistance and display quality, particularly due to the limitations of glass substrates and the difficulties in manufacturing with plastic substrates, which suffer from thermal expansion issues and retardation problems.
Innovation Solution
The use of a plastic substrate with a resin insulating layer composed of polybenzoxazole, polyamideimide, or polyimide containing an alicyclic structure, which has a thickness of 20 μm to 150 μm, a high weight loss temperature, and high transmittance, along with a wire grid polarizer, to form a liquid crystal display device that maintains strength and reduces manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a glass substrate is used for the insulating substrate, then the heat resistance is high (about 600°C), but the weight is large and the thickness cannot be reduced to 0.5 mm or less without cracking
Solution Approach 1:
The patent changes the material parameter from glass to plastic substrate, which fundamentally alters the thermal properties. The plastic substrate has lower heat resistance but enables weight reduction and thickness reduction to 0.5 mm or less, resolving the contradiction between heat resistance and weight/thickness reduction
Solution Approach 2:
The patent uses a composite structure with a plastic substrate combined with a heat-resistant resin layer (polyimide or polyamide imide) having a glass transition temperature of 250°C or higher. This composite approach maintains adequate heat resistance while achieving weight and thickness reduction
2Weight of stationary object
If the thickness of the insulating substrate is reduced to decrease weight, then the weight decreases, but the substrate tends to crack during manufacture or use when using glass substrates
Solution Approach 1:
The patent changes the material from glass to plastic, which fundamentally improves flexibility and crack resistance. Plastic substrates can be made thinner without cracking due to their inherent flexibility, resolving the contradiction between weight reduction and crack resistance
Solution Approach 2:
The patent employs a flexible plastic substrate that can be manufactured at thin dimensions (0.5 mm or less) without cracking. The flexibility of the plastic material allows for thin-film construction while maintaining structural integrity and reliability
3Weight of stationary object
If a plastic substrate is used to reduce weight and improve flexibility, then the weight decreases and the display surface can be formed in curved surfaces, but the heat resistance is insufficient (about 200°C) for thin-film transistor manufacturing requiring 300°C or higher
Solution Approach 1:
The patent creates a composite structure where a plastic substrate is combined with a heat-resistant resin layer (polyimide or polyamide imide) with glass transition temperature of 250°C or higher. This composite maintains the weight advantages of plastic while providing the necessary heat resistance for TFT manufacturing
Solution Approach 2:
The patent segments the substrate system into multiple functional layers: the plastic substrate provides flexibility and weight reduction, while a separate heat-resistant resin layer provides the necessary thermal stability for high-temperature processing
4Temperature
If a polyimide type resin is used for the insulating substrate, then the heat resistance is relatively high, but the resin is colored yellow to brown making it difficult to use for liquid crystal display panels
Solution Approach 1:
The patent uses a composite approach where a transparent or lightly colored heat-resistant resin layer is applied over the polyimide substrate. This allows the polyimide to provide heat resistance while the transparent overlay maintains display quality and light transmission
Solution Approach 2:
The patent applies different material properties to different layers: the polyimide substrate provides bulk heat resistance, while a separate transparent heat-resistant resin coating provides the optical quality needed for display applications, with each layer optimized for its specific function
5Weight of stationary object
If a plastic substrate is used, then the coefficient of thermal expansion is large (several tens to one hundred and several tens ppm/K), causing elongation at high temperatures and fluctuation of size or positional deviation
Solution Approach 1:
The patent uses a composite structure where the plastic substrate is combined with a heat-resistant resin layer. This composite structure helps control thermal expansion by distributing stress across layers with different expansion coefficients, reducing positional deviation during manufacturing
Solution Approach 2:
The patent modifies the thermal expansion parameter by selecting specific resin compositions and crosslinking densities to match the expansion characteristics of adjacent layers, minimizing differential expansion and maintaining manufacturing precision
Data Source
AI summary
An image display device having a display panel in which a first substrate and a second substrate are disposed to each other, in which the first substrate includes an insulating substrate composed of a resin, a circuit layer having a circuit where a plurality of Thin-film transistors are arranged in a matrix, and a polarizer disposed between the insulating substrate and the circuit layer, the insulating substrate has a thickness of 20 μm or more and 150 μm or less, a transmittance of 80% or more for a visible light at a wavelength of 400 nm or more and 800 nm or less, and a 3% weight reduction temperature of 300° C. or higher, and has no melting point or has a melting point of 300° C. or higher.